Discovery arrives back home at KSC – STS-129 ET/SRB mate

Discovery has returned to her home port of the Kennedy Space Center (KSC) on top of one of NASA’s Shuttle Carrier Aircraft (SCA). The two day cross country journey involved two stops in Texas, and an overnight stay in Louisiana. She joins her two sisters who are deep in processing for the next two missions, with STS-129 undergoing a processing milestone on Monday.

Planning for final leg required evaluations into unsettled weather over the flight path, before clearance was given not long after the scheduled departure time. With the NASA Pathfinder aircraft flying ahead, the best route back to Florida was picked for the SCA/Discovery duo, as they crossed over into Florida around 11am local time.

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The duo landed on the Shuttle Landing Facility (SLF) at around noon time, after a decision was made to cancel a flyaround of KSC due to poor weather closing in on the region.

The rest of the day involves demating Discovery from the top of the SCA at the Mate/Demate Device (MDD) located at the end of the SLF. Once raised off the SCA, the converted 747 will reverse clear, prior to Discovery being lowered on to her wheels for the tow back to her Orbiter Processing Facility (OPF).

Inside the home comforts of the OPF, Discovery will undergo further safing and post flight inspections – picking up on the procedures that began at Dryden.

A full review of her highly successful mission to the ISS is set to take place this Thursday, when the Program Requirements Control Board (PRCB) carry out the IFA (In Flight Anomaly) review – a required meeting which will also play a part in both the next scheduled shuttle mission (STS-129) Flight Readiness Review (FRR) and Discovery’s downstream STS-131 mission FRR.

Atlantis is currently undergoing closeouts – with recent issues relating to her Orbiter Docking System (ODS) now cleared – as her External Tank (ET-133) and the twin Solid Rocket Boosters (SRBs) undergo mating operations on Monday inside the Vehicle Assembly Building (VAB).

As noted in the processing update, inspections on Atlantis’ Fill and Drain Valves have been carried out, following issues with indications on Discovery’s LH2 PV12 valve during STS-128’s August 26th launch attempt.

There are four of these valves inside the MPS (Main Propulsion System), with the LO2 system housing the PV9 LO2 Outboard Fill/Drain Valve and PV10 LO2 Inboard Fill/drain. The LH2 System houses the PV11 LH2 Outboard Fill/Drain and the failed PV12 LH2 Inboard Fill/Drain.

The requirement for the nominal operation and cycling of the valve mainly relates to the ability to offload propellant in the event of – for instance – a pad abort, where detanking needs to take place in a timely manner. Offloading could still occur via the alternate PV11 route, but would take twice as long – which would be undesirable.

While the issue failed to repeat itself during the next launch attempt – and performed nominally – engineers are checking the valves on Atlantis to confirm the issue is not related to identical valves on the fleet.

“Inspection of the MPS fill-and-drain valves was performed,” added engineering notes. “For PV9 and PV11, the valve-position indicator is under evaluation by Engineering.”

The PV12 valve on Discovery will be replaced during her STS-131 flow, which was pre-scheduled due to the valve reaching the end of its operational lifetime.

L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.